In modern vehicles, and in particular in high performance cars, it is often preferable to fit alloy wheels as they offer many benefits in terms of the performance of the car. Alloy wheels for cars are made from an alloy of aluminium or magnesium, in contrast to standard wheels which are manufactured in steel. They are therefore considerably lighter than standard wheels.
The reduced weight of an alloy wheel carries the benefits of improving both the handling and the ride quality of the car, by lowering the total mass of components that are not supported by the suspension, or unsprung mass. In addition to lowering the unsprung mass of the car, the overall mass of the car is also reduced, which has associated benefits in terms of fuel economy. Finally, alloy wheels are generally considered to be more attractive than standard wheels, and also give the impression of high performance when fitted to a car, as their advantages are well known. It is therefore expected in the case of high performance cars that they should be fitted with alloy wheels. Clearly, when customers are paying a substantial sum of money for a high performance car, it will often be important to them that it is aesthetically pleasing. Therefore any additions or modifications to the alloy wheels will need to be sympathetic to this requirement.
Wheels of this type are generally shaped such that they feature a central hub, which attaches to the wheel axle, with a number of spokes extending from the hub to the outer rim to which the tyre attaches. Large gaps are left between the spokes, in order to reduce the mass of the wheel as much as possible. However, one problem that arises from this is that when the car is travelling at speed, these gaps between the spokes cause the air that is flowing past the wheel to become turbulent, and therefore significantly increase the drag effect of the air on the wheel and therefore the car as a whole. In more detail, the large gaps between the spokes enables the flow of air past the wheel to pass through the wheel easily, rather than maintaining its momentum in the direction parallel to the direction of travel of the vehicle. This means that the fuel economy of the car is compromised as well as the performance. One of the key considerations for modern cars is how efficiently they can run, so clearly there is a motivation to eliminate any source of drag on a car and improve its aerodynamic performance wherever possible. Furthermore, in order to achieve the objective of providing a lightweight wheel in which the amount of material used is minimised but in which the desired structural properties are achieved, the spokes are typically thin (in the radial sense of the wheel) and define a flat face which extends parallel to the axis of rotation of the wheel. Such a flat face results in increased air resistance when the wheel rotates.
It is an objective of the present invention to overcome or substantially mitigate the above mentioned problems.